The recently developed hardware and software, in a generalized resolution overlapping fashion, now allows 3-dimensional reconstruction of subcellular structures at both the light and electron microscopic levels. It is proposed to apply these 3-dimensional techniques to the structural determination of specific Drosophila polytene bands and interbands. This study will build on the recent molecular alignment of the Notch 5'regulatory and transcribed sequences to the interband and band of polytene locus 3C7 respectively. This study will start with further molecular band/interband alignments for diverse genetic loci with a superimposition of specific proteins localized by monoclonal and affinity purified polyclonal antibodies. A detailed, 3-dimensional reconstruction at both the optical and EM levels for specific bands/interbands will proceed. Specialized software will be written to interpret and compare the complicated images. Methods will be developed for the study in 3- dimensions of specific DNa probes in situ hybridized to bands/interbands. This polytene chromosome study will be extended by a 3-dimensional reconstruction of bands/interbands under conditions of biological modification. Transcription (puff formation) and specific chromosome aberrations (position-effect varigation and transvection) are examples for structural band/interband determinations.